1. Field of the Invention
This invention relates, in general, to heat exchangers and more particularly to heat exchangers which utilize vaporization of water for extracting heat from stove flues for space heating and humidification.
2. Description of the Prior Art
Stove flues are an essential part of free-standing stoves for the discharge of the flue gases and products of combustion. A free standing stove conventionally is connected to a chimney by means of a flue. In the discharge of flue gases into the atmosphere considerable amounts of heat are lost at large expense to the user.
Heat exchangers for extracting heat, otherwise lost, from flues are old in the art and are found in a variety of forms. The concentric pipe within pipe heat exchanger is perhaps the most simple form and has been used to great advantage in claiming the flue heat. To improve heat exchangers for economical reasons, new types of heat exchangers are constantly being developed. Much emphasis has been placed on cramming more heat transfer surface into less and less volume by the use of fin tubes, baffles, and the like as typified by U.S. Pat. No. 3,124,197 issued to R. S. Funk; U.S. Pat. No. 4,278,126 issued to F. M. Skrzypek; and U.S. Pat. No. 4,313,562 issued to R. H. White and by circuitous routing of either flue gases, room air, or both. Circuitous routing of flue gases interferes with the normal draw of the stove, often requires oversize flues, and may be dangerous in preventing escape of deadly gases. Circuitous routing of room air by fins, baffles, and the like often impede and restrict air flow causing whistling sounds, undersirable vibration of fin members, and clanking and rumbling where fins have worked loose. An alternative in preventing whistling or vibrations is to construct units which are ungainly large.
An additional problem with existing flue-type heat exchangers is the lack of conditioning of room air with moisture. When cool air is heated at constant specific humidity, the relative humidity is reduced and the effect is produced "dry" air. This circumstance is particularly is observed in extremely cold weather. Very dry air can cause discomfort to building occupants and is also unhealthful in causing chapping of lips, etc.